CN114761836A

CN114761836A - Optical layer and optical system

Info

Publication number: CN114761836A
Application number: CN202080084401.3A
Authority: CN
Inventors: 杨朝晖; 普热梅斯瓦夫·P·马克维茨; 马克·A·勒里希; 特里·D·彭; 塞雷娜·L·施洛伊斯纳; 大卫·A·罗森; 刘阳
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2019-12-06
Filing date: 2020-12-01
Publication date: 2022-07-15
Also published as: KR20220110783A; US20220397791A1; WO2021111297A1; JP2023505183A

Abstract

An optical system includes a lens layer including a plurality of microlenses arranged along orthogonal first and second directions; and at least one optically opaque mask layer spaced apart from the lens layer and defining a plurality of through openings therein arranged along the first direction and the second direction. There is a one-to-one correspondence between the microlenses and the openings such that for each microlens, the microlens and the corresponding opening are substantially centered on a straight line at the same oblique angle to the lens layer. The optical layer may include a lens layer and an optically opaque mask layer embedded in the optical layer.

Description

Optical layer and optical system

Background

A device including a liquid crystal display may include a fingerprint sensor behind the display.

Disclosure of Invention

In some aspects, the present disclosure provides an optical system comprising a lens layer comprising a plurality of microlenses arranged along orthogonal first and second directions; and at least one optically opaque mask layer spaced apart from the lens layer and defining a plurality of through openings therein arranged along a first direction and a second direction. There may be a one-to-one correspondence between the microlenses and the openings such that for each microlens, the microlens and the corresponding opening are substantially centered on a straight line at the same oblique angle to the lens layer. The optical layer may include a lens layer and an optically opaque mask layer embedded in the optical layer.

In some aspects, the present disclosure provides an optical system comprising: a lens layer including a plurality of microlenses arranged along orthogonal first and second directions; an optically opaque first mask layer spaced apart from the lens layer and defining a plurality of through first openings therein arranged along a first direction and a second direction; and an optically opaque second mask layer spaced apart from the lens layer and the first mask layer and defining a plurality of through second openings therein arranged along the first direction and the second direction. The first mask layer is disposed between the lens layer and the second mask layer. There is a one-to-one correspondence between the microlenses and the first and second openings such that for each microlens, the microlens and the corresponding first and second openings are substantially centered on a straight line at the same oblique angle to the lens layer. When image light carrying an image is incident on the microlens along a straight line with the image light substantially filling the microlens, greater than about 35%, or greater than about 40%, or greater than about 45%, or greater than about 50% of the incident image light is transmitted by the second opening. At least one of the first opening and the second opening is sized so as to reduce image quality degradation due to the microlens.

In some aspects, the present disclosure provides an optical layer comprising: a structured first major surface and an opposing second major surface, the structured first major surface comprising a plurality of microlenses arranged along orthogonal first and second directions; and an embedded optically opaque first mask layer disposed between and spaced apart from the first and second major surfaces. The first mask layer defines a plurality of through first openings therein arranged along a first direction and a second direction. There may be a one-to-one correspondence between the microlenses and the first openings. For each of at least a majority of the first openings, the first openings define a voided region having a maximum thickness greater than an average thickness of the first mask layer.

In some aspects, the present disclosure provides an optical layer comprising: a structured first major surface and an opposing second major surface, the structured first major surface comprising a plurality of microlenses arranged along orthogonal first and second directions; and an embedded optically opaque first mask layer disposed between and spaced apart from the first and second major surfaces. The first mask layer defines a plurality of through first openings therein arranged along a first direction and a second direction. There may be a one-to-one correspondence between the microlenses and the first openings. For each of at least a majority of the first openings, the first opening defines a voided region having a top major surface facing the first major surface and an opposing bottom major surface facing the second major surface. In a cross-section of the optical layer that is substantially perpendicular to the optical layer, the optical layer includes a plurality of nanoparticles concentrated along at least one of the top major surface and the bottom major surface of the voided region. In some embodiments, the first masking layer comprises a first material and the nanoparticles comprise at least one of the first material or an oxide of the first material.

In some aspects, the present disclosure provides an optical layer comprising: a structured first major surface and an opposing second major surface, the structured first major surface comprising a plurality of microlenses arranged along orthogonal first and second directions; and an embedded optically opaque first mask layer disposed between and spaced apart from the first and second major surfaces. The first mask layer defines a plurality of through first openings therein arranged along a first direction and a second direction. There may be a one-to-one correspondence between the microlenses and the first openings. For each of at least a majority of the first openings, the first opening defines a voided region having a top major surface facing the first major surface and an opposing bottom major surface facing the second major surface. In a cross-section of the optical layer that is substantially perpendicular to the optical layer, the top and bottom surfaces are spaced closer to the center of the voided region by a greater distance than the edges of the voided region. At least one of the top major surface and the bottom major surface may have a surface roughness in a range of 10nm to 200 nm.

In some aspects, the present disclosure provides a method of manufacturing an optical layer. The optical layer may be any of the optical layers described elsewhere herein. The method may include illuminating the embedded optically opaque mask layer through a plurality of microlenses to form a plurality of through first openings in the mask layer.

In some aspects, the present disclosure provides an optical system comprising an optical element and a refractive component. The optical element includes a lens layer including a plurality of microlenses arranged along orthogonal first and second directions; and an optically opaque first mask layer spaced apart from the lens layer and defining a plurality of through first openings therein arranged along the first and second directions. There is a one-to-one correspondence between the microlenses and the first openings such that for each microlens, the microlens and the corresponding first opening are substantially centered on a straight line. Each line is at the same oblique angle to the lens layer. The refractive component extends along a first direction and a second direction and is arranged in the vicinity of the optical element such that, for at least one first light beam incident on the refractive component along a third direction substantially orthogonal to the lens layer, the refractive component splits the first light beam into 2 to 9 beam segments leaving the refractive component along respective 2 to 9 main directions. A first main direction of the 2 to 9 main directions is substantially parallel to each straight line.

In some aspects, the present disclosure provides an optical system comprising a refractive component, an optical element, a light source, and an optical sensor. The refractive component extends along orthogonal first and second directions such that, for at least one first light beam incident on the refractive component along a third direction substantially orthogonal to the first and second directions, the refractive component splits the first light beam into 2 to 9 beam segments exiting the refractive component along respective 2 to 9 principal directions. The 2 to 9 main directions comprise the first main direction. The optical element is arranged in the vicinity of the refractive component such that at least 45% of the light in a beam segment incident on the optical element along the first main direction (but not any other main direction) is transmitted through the optical element. The light source is arranged to emit light in a direction substantially parallel to a second main direction of the 2 to 9 main directions. The optical sensor is arranged to receive light transmitted through the optical element along the first main direction.

Drawings

FIG. 1 is a schematic cross-sectional view of an optical system;

2A-2C schematically illustrate light incident on a microlens;

FIG. 3 is a schematic graph of an intensity distribution of light transmitted through a microlens;

FIG. 4 is a schematic cross-sectional view of an optical element or layer;

FIGS. 5A-5D are schematic cross-sectional views of portions of optical elements or layers;

FIG. 6 is a schematic cross-sectional view of an optical system including an optical element or layer;

FIG. 7 is a schematic top plan projection view of a microlens array and through openings;

FIGS. 8-9 are schematic cross-sectional views of an optical system;

FIGS. 10A-10B are schematic diagrams of maximum projected areas of an optical element and a refractive component;

FIG. 11 is a schematic cross-sectional view of a refractive component;

FIGS. 12A-12C are schematic conoscopic graphs;

FIG. 13A is a schematic cross-sectional view of an optical element or layer including microlenses and optical decoupling structures;

FIG. 13B is a schematic cross-sectional view of the optical element or layer of FIG. 13A attached to an adjacent layer;

FIG. 14 is a schematic cross-sectional view of an optical element or layer comprising two or more microlenses;

FIGS. 15-17 are graphs of calculated point spread functions for an optical system; and is

Fig. 18-20 are images of cross-sections through openings in an embedded mask layer.

Detailed Description

In the following description, reference is made to the accompanying drawings, which form a part hereof and in which is shown by way of illustration various embodiments. The figures are not necessarily to scale. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present description. The following detailed description is, therefore, not to be taken in a limiting sense.

For some applications, such as smart phone or tablet computer applications, it is desirable to place the fingerprint sensor behind a Liquid Crystal Display (LCD). However, liquid crystal displays typically include a refractive component, such as crossed prism films, behind the liquid crystal display panel. The light reflected from the fingerprint is typically split into a plurality of beam segments by the refractive component, and this may reduce the quality of the optical image of the fingerprint when incident on the sensor. According to some embodiments, optical elements, layers and systems are provided that avoid or substantially reduce such image quality degradation.

Fig. 1 is a schematic cross-sectional view of an optical system 150 including a lens layer 110, an optically opaque first mask layer 120, and an optically opaque second mask layer 125. In some implementations, the optical element or layer 100 includes a lens layer 110 and each of a first mask layer 120 and a second mask layer 125. The optical element or layer 100 can have a structured first major surface 103 and an opposing second major surface 104. In other embodiments, different optical elements may include one or more of the different layers. For example, a first optical element may include the lens layer 110 and the first mask layer 120, and a second optical element spaced apart from the first optical element may include the second mask layer 125.

The lens layer 110 includes a plurality of microlenses 102 arranged (e.g., in a regular array) along orthogonal first and second directions (x-and y-directions). The optically opaque first mask layer 120 is spaced apart from the lens layer 110 by a distance d1, which may be in the range of 2 microns to 35 microns, for example. The optically opaque first mask layer 120 defines a plurality of through first openings 122 therein arranged along a first direction and a second direction. The optically opaque second mask layer 125 is spaced apart from the lens layer 110 and the first mask layer 120 and defines a plurality of through second openings 127 therein arranged along the first direction and the second direction. The first mask layer 120 is disposed between the lens layer 100 and the second mask layer 125. The second mask layer 125 is spaced apart from the first mask layer 120 by a distance d2, which may be, for example, in the range of 1 micron to 20 microns. In some embodiments, d2< d1, or d2<0.7d1, or d2<0.5d 1. There may be a one-to-one correspondence between the microlenses 102 and the first and second openings 122, 127 (i.e., one first opening 122 and one second opening 127 for each microlens 102 corresponds to a microlens), such that for each microlens 102, the microlens and the corresponding first and

second openings

122, 127 are substantially centered on a line 140 that is at the same oblique angle θ from the lens layer 110. For example, the microlens 102a corresponds to the first opening 122a and the second opening 127a, and the microlens 102a and the corresponding first opening 122a and the second opening 127a are substantially centered on the straight line 140 a. For example, a lens or opening may be described as being substantially centered on a straight line 140 when a line passes through the center of the lens or opening or within about 20%, or within about 10%, or within about 5% of the diameter of the lens or opening, respectively, through the center.

Microlenses are typically lenses having at least two orthogonal dimensions (e.g., height and diameter, or diameters along two axes) less than 1mm and greater than 100 nm. For example, the microlenses may have an average diameter in the range of 10 micrometers to 100 micrometers. For example, the microlenses may have an average radius of curvature in a range of 5 to 50 micrometers. For example, the microlens may be a spherical microlens or an aspherical microlens. It has been found that aspheric microlenses can provide improved optical properties (e.g., improved focusing) for light incident at a desired off-axis angle (e.g., along line 140). For example, optical element or layer 100 or other optical elements or layers described elsewhere herein can have a total thickness in a range of 10 microns to 100 microns.

The mask layer may be described as optically opaque when less than 20%, or less than 15%, or less than 10%, or less than 5%, or less than 3% of unpolarized visible light normally incident on the layer in the regions between the openings is transmitted through the layer. The mask layer may be optically absorptive or optically reflective. Suitable mask layers include metal layers (e.g., vapor deposited or sputtered), metal oxide layers, coatings of dark materials (e.g., including optically absorbing dyes), and optically absorbing or reflecting films. The mask layer may have a sufficient thickness to render the material suitably optically opaque. For example, the average thicknesses t and t' of the mask layer may each be in the range of 5nm to 5 micrometers. In some embodiments, t and/or t' is in the range of, for example, 10nm to 500nm, or 10nm to 150nm, or 15nm to 100nm, or 15nm to 50nm, or 20nm to 40 nm.

A first masking layer 120 and a second masking layer 125 may be included to limit light transmitted through the optical element to light substantially only along line 140. A second mask layer 125 may be included to reduce crosstalk if light incident on one microlens is transmitted through an opening corresponding to another microlens. For example, light 108 that would otherwise cause crosstalk is blocked by second mask layer 125. In some embodiments, second mask layer 125 is omitted. In some embodiments, a pixelated photosensor can be used in place of the second mask layer 125, as further described elsewhere herein. Related optical elements are described in international application No. ib2019/056781(Yang et al).

In some embodiments, the first opening 122 is a physical opening. The physical opening has a material: the material is removed from the mask layer so that physical holes are present. For example, physical openings or holes may be formed in the optically opaque layer by laser ablation. In some embodiments, the first opening is an optical opening. The optical opening has a material: the material is treated so that light is transmitted through the optical opening even if the material is present in the optical opening. For example, the optical openings may be formed in the optically opaque layer by bleaching (e.g., the optically opaque layer incorporating the dye may be photobleached or thermally bleached so that the bleached dye is no longer optically absorbed). Optical apertures may be formed in birefringent reflective films by reducing birefringence in the apertures, as generally described in U.S. patent No.9,575,233(Merrill et al). An absorptive overcoat can optionally be applied to the optical film to increase the absorption of energy from the laser. In some embodiments, the second opening 127 is a physical opening. In some embodiments, the second opening 127 is an optical opening. In some embodiments, the average diameter d of the first openings 122 ranges, for example, from 500nm to 50 microns, or from 1 micron to 40 microns, or from 2 microns to 30 microns, or from 3 microns to 20 microns, or from 5 microns to 15 microns. In some embodiments, the average diameter d' of the second openings 127 ranges, for example, from 500nm to 50 microns, or from 1 micron to 40 microns, or from 2 microns to 30 microns, or from 3 microns to 20 microns, or from 5 microns to 15 microns.

In some embodiments, for each of at least a majority of the first openings 122, the first openings define a voided region. The voided region can have a top major surface facing the first major surface 103 and an opposite bottom major surface facing the second major surface 104. In some embodiments, in a cross-section of the optical layer substantially perpendicular to the optical layer, the optical layer comprises a plurality of nanoparticles concentrated along at least one of the top major surface and the bottom major surface of the voided region, as further described elsewhere. In some embodiments, in a cross-section of the optical layer that is substantially perpendicular to the optical layer, the top and bottom surfaces are spaced closer to the center of the voided region than the edges of the voided region. In some such embodiments, or in other embodiments, at least one of the top major surface and the bottom major surface has a surface roughness in a range from 10nm to 200nm, or in a range described elsewhere.

In some embodiments, the additional layer 244 is disposed on the second mask layer 125 opposite the first mask layer 120. In other embodiments, the additional layer 244 is omitted. In some embodiments, for each of at least a majority of the second openings 127, the second openings define a voided region. The voided region can have a top major surface facing the first major surface 103 and an opposite bottom major surface facing the second major surface 104. In some embodiments, in a cross-section of the optical layer substantially perpendicular to the optical layer, the optical layer comprises a plurality of nanoparticles concentrated along at least one of the top major surface and the bottom major surface of the voided region, as further described elsewhere. In some embodiments, in a cross-section of the optical layer that is substantially perpendicular to the optical layer, the top and bottom surfaces are spaced closer to the center of the voided region than the edges of the voided region. In some such embodiments, or in other embodiments, at least one of the top major surface and the bottom major surface has a surface roughness in a range from 10nm to 200nm, or in a range described elsewhere.

In some embodiments, additional layers are included. For example, additional layers (such as primer layers or tie layers) may be disposed at any one or more interfaces between adjacent layers depicted in fig. 1 in order to improve bonding between adjacent layers.

For convenience in description, spatially relative terms (including, but not limited to, "top," "bottom") are used to describe a spatial relationship of an element relative to another element. Such spatially relative terms encompass different orientations of the device in use or operation in addition to the particular orientation depicted in the figures and described herein. For example, if the object depicted in the drawings is turned over or flipped over, portions previously described as below or beneath other elements would then be above those other elements.

Fig. 2A is a schematic illustration of light 130 incident on a microlens 102, according to some embodiments. Fig. 2B is a schematic illustration of light 130 incident on a microlens 102, where the microlens causes image quality degradation, according to some embodiments. Fig. 2C is a schematic illustration of light 130 incident on the microlens 102, wherein at least one of the first opening 122 and the second opening 127 is sized so as to reduce image quality degradation due to the microlens. In some embodiments, when image light 130 carrying an image 133 is incident on the microlens 102 along a straight line 140 with the image light 130 substantially filling the microlens 102, greater than about 35%, or greater than about 40%, or greater than about 45%, or greater than about 50% of the incident image light is transmitted by the second opening 127. In some implementations, at least one of the first opening 122 and the second opening 127 is sized so as to reduce image quality degradation due to the microlenses. For example, image light may be described as substantially filling a microlens when the image light fills the microlens, or when the image light fills at least 70%, or at least 80%, or at least 90% of the outer surface area of the microlens.

Fig. 3 is a schematic graph of an intensity distribution at a nominal image plane of light transmitted through a microlens causing image quality degradation. The diameter D of the opening in the mask layer is shown, which is sized in order to reduce image quality degradation due to the micro-lenses. For example, when the surface of the microlens deviates from an ideal shape due to manufacturing constraints, the microlens may cause image quality degradation. For example, a tool used to form a microlens may have a surface formed by removing material from a layer that produces a plurality of facets that approximate, but do not precisely follow, the ideal shape of the microlens.

In some embodiments, the optical system is configured to detect a fingerprint. Light propagating through the optical system from any point at the front surface of the display panel preferably has a limited spatial extent when incident on the fingerprint sensor in order to form a desired (e.g., suitably sharp) fingerprint image. This spatial extent can be quantified by the point spread function of the optical system. The larger the spatial spread of the point spread function, the more blurred the fingerprint image. According to some embodiments, it has been found that including an optical element as described herein in an optical system can reduce the width of the point spread function. In some embodiments, the optical system has a point spread function for light incident on the optical system from a lambertian point source, the point spread function having a full width at half maximum (FWHM) of less than about 300 microns, or less than about 200 microns, or less than about 150 microns, or less than about 100 microns at an optical sensor disposed behind the optical element (see, e.g., fig. 8-9).

As further described elsewhere herein (see, e.g., fig. 8-9), in some embodiments, the optical element 100 (e.g., or 300) includes the lens layer 110 and the first and second mask layers 120 and 125, and the optical system 150 further includes: a refractive component 160 extending along the first and second directions and arranged in the vicinity of the optical element 100 such that for at least one first light beam 230 incident on the refractive component along a third direction (-z direction) substantially orthogonal to (e.g. within 30 degrees, or within 20 degrees, or within 10 degrees) the lens layer 110, the refractive component splits the first light beam into 2 to 9

beam segments

112, 114 leaving the refractive component along respective 2 to 9

principal directions

131, 132, a first principal direction 131 of the 2 to 9 principal directions being substantially parallel (e.g. within 30 degrees, or within 20 degrees, or within 10 degrees) to each straight line 140. For example, the at least one first light beam 230 may be any light beam having a width greater than the width of the prism (or other refractive element) in the refractive component. Other beams of narrower width may be split into less than 2 to 9 main directions. Each beam segment is a transmitted portion of the incident beam that propagates in substantially the same direction, referred to as the primary direction. The beam segments and principal directions can be identified from conoscopic plots of transmitted light intensity, e.g., as described further elsewhere herein (see, e.g., fig. 12A-12C).

In some embodiments, optical system 150 further includes a liquid crystal display 270 extending along the first direction and the second direction, a light guide 265 disposed to illuminate the liquid crystal display, a refractive member 160 disposed between liquid crystal display 270 and light guide 265, and an optical sensor 145 disposed adjacent light guide 265 opposite liquid crystal display 270 (see, e.g., fig. 9). In some embodiments, the optical element 100 (e.g., or 300) including the lens layer 110 and the first and second mask layers 120 and 125 is disposed between the light guide 265 and the optical sensor 145 such that the second mask layer 125 faces the optical sensor 145 (e.g., for the optical element 300 oriented as indicated by the x-y-z coordinate system of fig. 1 and 8, the optical element or layer 100 of fig. 1 may be placed as shown in fig. 8).

In some embodiments, each sub-layer of the optical element 100 (e.g., the lens layer 110, the first mask layer 120, and the second mask layer 125) is bonded to an adjacent layer of the optical element 100. In such embodiments, the optical element 100 may be referred to as an optical layer. In some implementations, the first mask layer 120 is embedded in the optical layer. In some embodiments, the additional layer 244 is disposed on the second mask layer 125 opposite the first mask layer 120, such that the second mask layer 125 is also an embedded layer. In some embodiments, second mask layer 125 may be omitted.

Fig. 4 is a schematic cross-sectional view of an optical element or layer 200. In some embodiments, the optical element or layer 200 includes a structured first major surface 103 and an opposing second major surface 104, wherein the structured first major surface 103 includes a plurality of microlenses 102 arranged along orthogonal first and second directions (x-and y-directions). The optical layer further comprises an embedded optically opaque first mask layer 120 disposed between and spaced apart from the first and second

major surfaces

103, 104. The first mask layer 120 defines therein a plurality of through first openings 122 arranged along a first direction and a second direction. There may be a one-to-one correspondence between the microlenses and the first openings. In some embodiments, for each of at least a majority of the first openings 122, the first openings define a voided region 123.

In some embodiments, the optical element or layer 200 is prepared by micro-replicating the plurality of microlenses 102 using, for example, a cast and Ultraviolet (UV) curing process in which a resin is cast onto a substrate and cured in contact with the replication tool surface, as generally described in U.S. Pat. nos. 5,175,030(Lu et al), 5,183,597(Lu) and 9,919,339(Johnson et al), and U.S. patent application publication No.2012/0064296(Walker, JR. et al). An optically opaque first mask layer 120 can then be formed by, for example, applying an opaque material onto a major surface 143 of the microlens substrate opposite the first major surface 103. The opaque material may have a sufficient thickness to render the material suitably optically opaque. For example, the opaque material may be 10nm to 5 microns thick. In some embodiments, the opaque material is aluminum having a thickness of 10nm to 500nm (e.g., 15nm to 150nm, or 15nm to 100nm, or 20nm to 50nm), which can be coated using, for example, standard magnetron sputtering. The additional layer 144 may be coated or laminated onto the opaque material layer. An optional second masking layer may then be deposited over the additional layer 144, if desired. An optional second additional layer can then be disposed on the second mask layer opposite the additional layer 144, if desired. The openings 122 may then be formed by, for example, laser ablation through the microlenses 102. Suitable lasers include, for example, fiber lasers with an operating wavelength of 1070nm, such as 40W pulse fiber lasers. In some embodiments, layer 120 is formed by applying a reflective multilayer optical film to major surface 143. Physical or optical through openings may then be formed in the optical film by irradiating with laser light through the microlenses. The use of a laser to form holes in a layer through a microlens array is generally described, for example, in US2007/0258149(Gardner et al). Other suitable methods of forming the openings include microprinting and photolithographic techniques (e.g., including using a microlens layer to expose a photolithographic mask).

In some embodiments, methods of making an optical layer are provided. The method can include providing a first layer including a structured first major surface 103 and an opposing second major surface 104. The structured first major surface 103 comprises a plurality of microlenses 102 arranged along orthogonal first and second directions. The first layer includes an embedded optically opaque first mask layer disposed between and spaced apart from the first and second major surfaces. The method may further include irradiating the first mask layer through the plurality of microlenses 102 to form a plurality of through first openings 122 arranged along the first direction and the second direction in the first mask layer. There may be a one-to-one correspondence between the microlenses and the first openings. In some embodiments, the first layer further comprises an optically opaque second mask layer, wherein the first mask layer is disposed between and spaced apart from the first major surface 103 and the second mask layer. The irradiating the first mask layer step may further include irradiating the second mask layer through the plurality of microlenses 102 and through the first mask layer to form a plurality of penetrating second openings 127 arranged along the first direction and the second direction in the second mask layer. There may be a one-to-one correspondence between the microlenses 102 and the second openings 127.

Fig. 5A-5D are schematic cross-sectional views of regions in an optical element or layer near an embedded optically opaque first mask layer 120, according to some embodiments. In some embodiments, for each of at least a majority of the first openings 122, the first openings define a voided region 723 having a maximum thickness h that is greater than the average thickness t of the first mask layer 120. In some embodiments, the first mask layer 120 has an average thickness t, the first openings 122 have an average maximum lateral dimension d, and t/d <0.05, or t/d <0.01, or t/d < 0.005. In some embodiments, for each of at least a majority of the first openings, the voided

region

123 or 723 extending through the first opening is substantially laterally coextensive with the first opening. When the voided region fills at least 60% (or at least 70%, or at least 80%, or at least 90%) of the total area of the first opening, the voided region can be described as being substantially laterally coextensive with the first opening. Fig. 5A is a schematic cross-sectional view of a portion of an optical layer including a mask layer 120 that includes an opening 122 and a voided region 723 that is laterally coextensive with the opening 122. Fig. 5B is a schematic cross-sectional view of a portion of an optical layer including a mask layer 120 that includes an opening 122 and a voided region 723 that is substantially laterally coextensive with, but not completely laterally coextensive with, the opening 122. The voided regions are regions where solid material has been removed. Air or gas may be present in the voided region.

In some embodiments, voided region 723 has a top major surface facing first major surface 103 and an opposite bottom major surface facing second major surface 104, wherein in a cross-section of the optical layer substantially perpendicular to the optical layer, the top and bottom surfaces have a spacing h1 (see fig. 5C) closer to the center of the voided region that is greater than a spacing h2 closer to the edges of the voided region, wherein h1> h 2. At least one of the top major surface and the bottom major surface may have a surface roughness R. For example, the surface roughness R may be at least 10nm, or at least 12nm, or at least 15nm, or at least 20 nm. For example, the surface roughness R may be no more than 200nm, or no more than 150nm, or no more than 120 nm. The surface roughness may be caused by laser ablation of the mask layer. For example, laser ablation of the mask layer can roughen the surface of the voided regions 723 by depositing nanoparticles along the surface. Surface roughness refers to the average deviation of a surface from an average smooth surface.

In some embodiments, for each of at least a majority of the first openings 122, the first opening defines a voided region 723 having a top major surface 171 facing the first major surface 103 and an opposite bottom major surface 173 facing the second major surface 104. In some embodiments, as schematically shown in fig. 5D, the optical layer includes a plurality of nanoparticles 177 concentrated along at least one of the top major surface 171 and the bottom major surface 173 of the voided region (e.g., in a cross-section of the optical layer substantially perpendicular to the optical layer). In some embodiments, in a cross-section of the optical layer that is substantially perpendicular to the optical layer (e.g., in the x-z cross-section schematically shown in fig. 5D), top surface 171 and bottom surface 173 are spaced more closely to the center of the voided region than to the edge of voided region 723 (e.g., as schematically shown in fig. 5A, where the spacing near the center is h and the spacing near the edge is about t, or as schematically shown in fig. 5C, where h1> h 2). The surface roughness of at least one of the top major surface and the bottom major surface may be in the range of 10nm to 200nm or in ranges described elsewhere.

In some embodiments, top surface 171 and bottom surface 173 are substantially concave toward one another (e.g., concave toward one another along greater than 50%, or at least 60%, or at least 70% of the area of one or both of the surfaces).

In some embodiments, the first mask layer 120 comprises a first material and the nanoparticles 177 comprise at least one of the first material or an oxide of the first material. In some embodiments, the first material is a metal. Any suitable metal may be used for the first material. For example, the metal may be aluminum, titanium, chromium, zinc, tin, tungsten, gold, silver, or alloys thereof. In some embodiments, the nanoparticles comprise an oxide of a metal. For example, the nanoparticles may include aluminum oxide, titanium oxide, chromium oxide, zinc oxide, or combinations thereof. In some embodiments, nanoparticles 177 are or comprise aluminum and aluminum oxide. In some embodiments, nanoparticles 177 comprise alumina at greater than about 50 wt%.

In some embodiments, at least 90% of the nanoparticles 177 have an average diameter less than about 150nm, or less than about 100 nm. In some embodiments, at least 90% of the nanoparticles have an average diameter greater than about 1nm, or greater than about 5nm, or greater than about 10 nm. The average diameter of a nanoparticle is the diameter of a sphere having a volume equal to the volume of the nanoparticle.

In some embodiments, the optical layer includes a first polymer layer disposed between the first major surface and the mask layer, and a second polymer layer disposed between the mask layer and the second major surface. In some embodiments, at least one of the first polymer layer and the second polymer layer comprises a plurality of second nanoparticles uniformly dispersed therein. For example, a second nanoparticle may be included to increase the refractive index of the layer as known in the art (see, e.g., U.S. patent No.8,202,573(Pokorny et al)).

In some embodiments, the optical element or layer 200 schematically illustrated in fig. 4 further comprises an optically opaque second mask layer 125 (see, e.g., fig. 1) defining a plurality of through second openings 127 therein arranged along a first direction and a second direction, wherein the first mask layer 120 is disposed between and spaced apart from the first major surface 103 and the second mask layer 125, wherein there may be a one-to-one correspondence between the microlenses and the second openings. In some embodiments, for each microlens, the microlens and the corresponding first opening and second opening are substantially centered on a line at the same oblique angle to the first mask layer. The first opening and/or the second opening may be as described elsewhere (see, e.g., fig. 5A-5D).

Fig. 6 is a schematic cross-sectional view of an optical element or layer 200 disposed on a photosensor 225. In some embodiments, the optical system 250 includes an optical element or layer 200 and a photosensor 225 including a plurality of sensor pixels 227. In some implementations, there is a one-to-one correspondence between the microlenses 102 and the sensor pixels 227, such that for each microlens in at least a majority of the microlenses 102, the microlens 102 and the corresponding first opening 122 and sensor pixel 227 are substantially centered on a line 140 that is at the same oblique angle θ as the first mask layer 120.

Fig. 7 is a schematic top-down projection view of a plurality of microlenses 102 and through openings 126 (e.g., corresponding to first through openings 122 or second through openings 127). The microlenses 102 are arranged along orthogonal first and second directions (x-and y-directions), and the openings 126 are arranged along the first and second directions. In the embodiment shown, the microlenses 102 and through openings 126 are located on a regular triangular array. Other patterns are also possible (e.g., square or rectangular arrays, other periodic arrays, or irregular patterns).

Fig. 8 is a schematic diagram of an optical system 350 according to some embodiments. Fig. 9 is a schematic diagram of some embodiments of an optical system 350.

In some embodiments, optical system 350 includes optical element 300 (e.g., corresponding to 100 or 200) and refractive component 160. The optical element 300 includes a lens layer 110 including a plurality of microlenses arranged along orthogonal first and second directions (x-and y-directions); and an optically opaque first mask layer 120 spaced apart from the lens layer 110 and defining a plurality of through first openings therein arranged along the first and second directions. In some embodiments, there is a one-to-one correspondence between the microlenses and the first openings such that for each microlens, the microlens and the corresponding first opening are substantially centered on a straight line 140, wherein each straight line is at the same oblique angle θ to the lens layer 110. In some embodiments, the refractive component 160 extends along the first direction and the second direction and is disposed proximate the optical element such that for at least one first light beam 230 incident on the refractive component along a third direction (the-z direction) substantially orthogonal to the lens layer, the refractive component 160 splits the first light beam into 2 to 9 beam segments 665 (see, e.g., fig. 12A-12C) exiting the refractive component along respective 2 to 9 principal directions 667 (see, e.g., fig. 12A-12C), wherein a first principal direction 131 of the 2 to 9 principal directions is substantially parallel to each straight line 140.

In some embodiments, the optical element 300 further includes an optically opaque second mask layer 125 spaced apart from the lens layer 110 and the first mask layer 120 and defining a plurality of through second openings 127 therein arranged along the first direction and the second direction, wherein the first mask layer 120 is disposed between the lens layer 110 and the second mask layer 125 (see, e.g., fig. 1). In some embodiments, there is a one-to-one correspondence between the microlenses and the second openings, such that for each microlens 102a and corresponding straight line 140a, the microlens 102a and corresponding first and

second openings

122a and 127a are substantially centered on the straight line 140.

In some embodiments, the optical system 350 further includes a photosensor 225 adjacent to the optical element 300 (see, e.g., fig. 6). As further described elsewhere herein, the photosensor 225 can include a plurality of sensor pixels. There may be a one-to-one correspondence between the microlenses and the sensor pixels such that for each microlens and corresponding straight line, the microlens and corresponding first opening and sensor pixel are substantially centered on the straight line 140.

In some embodiments, for each microlens in at least a majority of the plurality of microlenses, at least two of the

beam segments

112, 114 are incident on the microlens, wherein at least two of the

beam segments

112, 114 include a first beam segment 112 propagating along a first principal direction 131. In some embodiments, at least 30%, or at least 40%, or at least 45%, or at least 50%, or at least 55% of the light in the beam segment incident on the optical element 300 along the first principal direction 131 (but not any other principal direction) is transmitted through the optical element 300. In some embodiments, for each principal direction 132 other than the first principal direction 131, no more than 10%, or no more than 5%, of the light in the beam segment incident on the optical element 300 along the principal direction is transmitted through the optical element.

In some embodiments, optical system 350 includes a refractive component 160 that extends along orthogonal first and second directions such that, for at least one first light beam 230 incident on refractive component 160 along a third direction substantially orthogonal to the first and second directions, the refractive component splits the first light beam into 2 to 9 beam segments exiting the refractive component along respective 2 to 9 principal directions, wherein the 2 to 9 principal directions include first principal direction 131. In some embodiments, 2 to 9 primary directions define angles β therebetween, wherein each angle β is greater than about 30 degrees. In some embodiments, the refractive component 160 comprises a first prismatic film 252 comprising a first plurality of prisms 254 extending along a first longitudinal direction (x-direction) substantially parallel to the lens layer 110. In some embodiments, the refractive component 160 further comprises a second prismatic film 256 adjacent to the first prismatic film 252. The second prismatic film 256 may include a second plurality of prisms 258 extending along a second longitudinal direction (y-direction) that is substantially parallel to the lens layer 110 and substantially orthogonal to the first longitudinal direction.

The optical system 350 may further comprise an optical element 300 arranged in the vicinity of the refractive component 160 such that at least 45% (or any of the ranges described elsewhere herein) of light in a beam segment incident on the optical element 300 along the first principal direction 131 (but not any other principal direction 132) is transmitted through the optical element 300. The optical system 350 may further comprise a light source 139 and/or 141 arranged to emit light 142 and/or 147, respectively, in a direction substantially parallel to a second main direction of the 2 to 9 main directions. In some embodiments, the light source is an infrared light source. In some embodiments, optical system 350 includes an infrared diffuser. For example, an infrared diffuser may be positioned between the infrared light source and the touch surface of the display to improve the uniformity of the infrared light incident on the touch surface. The optical system 350 may further comprise an optical sensor 145 arranged to receive light transmitted through the optical element 300 along the first main direction 131. In some embodiments, the optical sensor 145 is an infrared light sensor. In some embodiments, the first and second primary directions are different (e.g., the first primary direction may be direction 131 and the second primary direction may be direction 132). In some embodiments, the first and second main directions are the same (e.g., the first and second main directions may each be direction 131).

Fig. 10A-10B are schematic diagrams of maximum projected areas of an optical element 300 and a refractive component 160 according to some embodiments. As schematically illustrated in fig. 10A, in some embodiments, the optical element 300 is substantially coextensive with at least a portion of the refractive component 160, wherein the maximum projected area of the portion of the refractive component 160 is at least about 30% of the maximum projected area of the refractive component 160. As schematically illustrated in fig. 10B, in some embodiments, the optical element 300 and the refractive component 160 are substantially coextensive. A layer or surface may be substantially coextensive with another layer or surface when at least 60%, or at least 70%, or at least 80%, or at least 90% of the total area of the layer or surface is coextensive with at least 60%, or at least 70%, or at least 80%, or at least 90% of the total area of the other layer or surface.

The number of primary directions may be determined by, for example, the number and shape of light redirecting films included in the refractive component 160. For example, at least one first light beam (e.g., a substantially normally incident light beam having a diameter greater than the width of the prisms) incident on a single prism film will result in two principal directions, while a first light beam incident on a crossed prism film will result in four principal directions. Fig. 11 is a schematic cross-sectional view of a truncated prism film 352 that includes a plurality of truncated prisms 354 arranged along a first direction (x-direction) and extending along an orthogonal second direction (y-direction). At least one first light beam incident on film 352 will be split into 3 beam segments, each corresponding to one facet of truncated prism 354. More generally, n non-vertical facets may result in n beam segments. Two crossed truncated prism films 352 would result in 9 principal directions. In some embodiments, the 2 to 9 major directions are 2, 4, or 9 major directions. In some embodiments, the 2 to 9 principal directions are 4 principal directions.

Fig. 12A-12C are conoscopic graphs illustrating a beam segment 665 and a primary direction 667. Each point in the conoscopic plot represents a direction (specified by azimuth and polar angles). The darker areas indicate higher intensity of transmitted light. Beam segment 665 is a region of higher intensity representing a light beam that propagates primarily along a principal direction 667, which can be considered to be the direction in which the intensity has a local maximum. In fig. 12A, there are two beam segments 665 that propagate in two principal directions 667; in fig. 12b, there are four beam segments 665 which propagate in four main directions 667; also in fig. 12C, there are nine beam segments 665 that propagate in nine principal directions 667.

In some embodiments, the microlens layer is bonded to the display panel through the low refractive index layer. In some embodiments, the low refractive index layer has a refractive index of no more than 1.3 (e.g., in the range of 1.1 to 1.3), and is disposed on and has a major surface that substantially conforms to the first major surface 103 of the lens layer 110. Refractive index refers to the refractive index at 633nm, unless otherwise indicated. The layer having a refractive index of not more than 1.3 may be a nanovoided layer such as described in U.S. patent application publication nos.2013/0011608(Wolk et al) and nos.2013/0235614(Wolk et al).

In some embodiments, the optical decoupling structures (also referred to as elongated spacing elements) are disposed on the first major surface 103 such that the optical decoupling structures can be bonded to an adjacent display panel with an adhesive layer, e.g., while creating air gaps between the microlenses and the adhesive layer.

Fig. 13A is a schematic cross-sectional view of an optical element 1300a (e.g., corresponding to 100, 200, or 300) that includes a layer 1360a having opposing first and second

major surfaces

1362, 1364 a. First major surface 1362 includes an array of microlenses 1350 and an array of optical decoupling structures 1355 extending from layer 1360a over the tops of microlenses 1350. For example, the optical decoupling structure 1355 may be a post. Each microlens in the microlens array 1350 is concave toward the second major surface 1364 a. Each optical decoupling structure 1357 of at least a majority of the array of optical decoupling structures 1355 is positioned between two or more

adjacent microlenses

1351 and 1352 in microlens array 1350 and extends over the two or more

adjacent microlenses

1351 and 1352 in a direction away from second major surface 1364a (e.g., the z-direction, see the x-y-z coordinate system shown in fig. 13A). For example, all of the optical decoupling structures in the array of optical decoupling structures 1355 may be positioned between two or more adjacent microlenses in the array of microlenses 1350, or all of the optical decoupling structures except for optical decoupling structures near corners or edges of the array of microlenses 1350 may be positioned between two or more adjacent microlenses.

In some embodiments, layer 1360a is a monolithic layer (e.g., formed with microlenses 1350 in, for example, a casting and curing process). In other embodiments, optical decoupling structure 1355 is printed onto the microlens layer such that the layers of the optical decoupling structure and the microlens layer are sublayers of layer 1360 a.

In some embodiments, the array of optical decoupling structures 1355 is adapted to substantially diverge, diffuse, reflect, or absorb light obliquely incident on the optical element 1300 a. This may be achieved, for example, by adding diffusing particles to the printed optical outcoupling structures, or by appropriately selecting the shape of the optical outcoupling structures (e.g. curvature of the side faces), or by applying a coating (e.g. a reflective coating) to the optical outcoupling structures. This may provide reduced cross talk between adjacent microlenses. For example, obliquely incident light rays 1303 may be transmitted through the optical decoupling structure and through a first microlens to an opening in a mask layer (see, e.g., fig. 13B) aligned with an adjacent microlens. Such crosstalk can be significantly reduced if the optical decoupling structure substantially diverges, diffuses, reflects or absorbs obliquely incident light. This schematically shows light ray 1308 being diffused by optical decoupling structures in the array of optical decoupling structures 1355, thereby reducing potential cross-talk.

The optical decoupling structure may be any object that protrudes beyond the microlens to attach to an adjacent layer such that the adjacent layer is not in contact with the microlens. The optical decoupling structure may be a cylindrical post, or may be a post having a non-circular cross-section (e.g., a rectangular, square, oval, or triangular cross-section). The optical outcoupling structures may have a constant cross section, or the cross section may vary in the thickness direction (for example, the optical outcoupling structures may be pillars tapered to thin near the tops of the pillars). In some embodiments, the optical outcoupling structure has a tapered elliptical cross-section. For example, the optical decoupling structure may have any of the geometries of the optical decoupling structures described in international application publication No. wo 2019/135190(Pham et al). In some embodiments, the optical decoupling structure extends from a base of the microlens array. In some embodiments, at least some of the optical decoupling structures are disposed on top of at least some of the microlenses.

Fig. 13B is a schematic cross-sectional view of an optical element 1300B that includes optical element 1300a and also includes layer 1360B.

Layers

1360a and 1360b together define a first layer having a first major surface 1362 and an opposing second major surface 1364 b. Optical element 1300b also includes a masking layer 1388 disposed on second major surface 1364 b. Masking layer 1388 is also indirectly disposed on second major surface 1364 a. An additional layer 1374 is disposed on mask layer 1388. An optional second mask layer can be disposed on the additional layer 1374 opposite the mask layer 1388, if desired.

Masking layer 1388 includes an array of through openings 1380, as further described elsewhere herein. Optical element 1300b also includes an adhesive layer 1343 adjacent first major surface 1362. Each optical decoupling structure 1355 at least partially penetrates through the adhesive layer 1343, and each microlens 1350 is completely separated from the adhesive layer 1343 by an air gap 1344. In the illustrated embodiment, the adhesive layer 1343 is attached to the display 1390.

In some embodiments, the optical element or layer includes two or more microlenses. Fig. 14 is a schematic cross-sectional view of an optical element or layer 400 (e.g., corresponding to 100, 200, or 300) having opposing first and second

major surfaces

103 and 104, wherein the first major surface 103 includes a first plurality of microlenses 102 and the second major surface 104 includes a second plurality of microlenses 202. The optical element or layer 400 includes an embedded optically opaque first mask layer 120 disposed between and spaced apart from the first and second

major surfaces

103, 104. The first mask layer 120 defines a plurality of first openings 122 therethrough. The

microlenses

102 and 202 can be formed on opposite sides of the mask layer 120 (e.g., embedded between polymer layers) using a casting and curing process, for example, where the

microlenses

102 and 202 are aligned, and after forming the

microlenses

102 and 202, the first opening 122 can be formed in the mask layer 120.

In some implementations, there is a one-to-one correspondence between the microlenses 102 and the first openings 122. In some implementations, the microlenses 102 and corresponding first openings 122 are substantially centered on a line 140 that is at the same oblique angle θ to the lens layer 110 or to the first mask layer 120. In some embodiments, there is a one-to-one correspondence between at least a majority of the microlenses 102 and at least a majority of the microlenses 202. In some implementations, there is a one-to-one correspondence between microlenses 102 and microlenses 202. In some embodiments, the microlenses 102 and corresponding first openings 122 and corresponding microlenses 202 are substantially centered on the straight line 140. In some embodiments, for each of at least a majority of the first openings 122, the first openings define a voided region 123. As described further elsewhere, the voided regions can have a maximum thickness that is greater than the average thickness of the first mask layer 120. For example, the microlens 102 may be used to focus light on the opening 122, and the microlens 202 may be used to collimate the light transmitted through the opening 122. In some embodiments, the optical element or layer 400 includes two spaced-apart mask layers disposed between the first major surface 103 and the second major surface 104 (see, e.g., fig. 1).

Examples

Examples 1-2 and comparative example C1

Optical modeling using LightTools ray tracing software (new thinking technology, Synopsis, inc., Mountain View, CA) was performed as follows. A lambertian point source is used to represent a fingerprint. In the model, crossed prism films were placed between the point source and the image sensor, an LCD display panel was placed between the point source and the crossed prism films, and an optical element similar to optical element or

layer

100 or 200 was placed between the crossed prism films and the image sensor, with the microlenses facing the crossed prism films and the mask layer facing the image sensor. The through opening is positioned such that light incident on the microlens at 52 degrees with respect to the normal to the plane of the optical element will pass through the optical element. The model parameters are as follows: the thickness of the LCD panel is 0.5 mm; the distance from the point source to the optical element is 1 mm; the radius of curvature of the microlenses was 25 microns; the distance from the top of the microlens layer to the first mask layer was 32 microns; when two mask layers are included, the spacing between the two mask layers is 5 microns; the diameter of the through opening is 3 micrometers; the refractive index of the microlens is 1.65; and the material of the mask layer was modeled as a perfect optical absorber.

Fig. 15 to 17 show the point spread functions determined for the case where the optical element includes two mask layers (embodiment 1), the case where the optical element includes only one mask layer (embodiment 2), and the case where the optical element is omitted (comparative example C1), respectively. When the optical element is included, the width of the point spread function is significantly reduced compared to the case where the optical element is omitted. The inclusion of two mask layers significantly reduces the point spread function compared to the case where a single mask layer is used.

Example 3

An optical element similar to optical element 100 was prepared as follows. A microlens layer was formed on a 0.92 mil thick PET substrate using a cast and cure process. The microlens layer is formed of an acrylic resin having a refractive index of about 1.69 at 532 nm. The microlenses had an average radius of curvature of about 17 microns and were disposed at a pitch of about 20 microns. A 30nm thick layer of aluminum was vacuum coated onto the PET substrate on the side substrate opposite the microlens layer, a 4 micron thick polymer layer was coated onto the aluminum layer and cured, a second 30nm thick layer of aluminum was vacuum coated onto the polymer layer, and a 1 micron thick polymer layer was coated onto the second aluminum layer and cured. A via is then formed in the aluminum layer by laser ablation through the microlens layer. A 40W SPI laser (SPI Lasers, Southampton, UK) from south ampton, england was used under the following conditions: 50% power, 7 x expander, 167mm F-theta lens, 30nm pulse length, 20kHz repetition rate, 2m/s scan speed and 100 micron pitch.

Sections of the resulting optical layer about 120nm thick were micro-dissected from the sample. Fig. 18 is a Transmission Electron Microscope (TEM) image of a cross section through an opening in the first mask layer 120, which is an embedded layer of the optical element 100. The voided regions 723 or air pockets created by the ablation process are visible in the image. Cracks in the mask layers 120 and 125 resulting from the microdissection process are visible. A region with voids is formed in the mask layer 125 outside the region shown in the figure. The maximum thickness of the voided region 723 is greater than the thickness of the first mask layer. Fig. 19 is a High Angle Annular Dark Field (HAADF) image of a cross-section through an opening in the first mask layer 120. Fig. 20 is a higher magnification image of a portion of fig. 19. The nanoparticles are visible at the opposite surface of the voided region. STEM-EDS (scanning transmission electron microscopy-energy dispersive spectroscopy) analysis showed that the nanoparticles were composed mainly of aluminum and oxygen.

Terms such as "about" will be understood by those of ordinary skill in the art in the context of the use and description herein. If the use of "about" in the context of the use and description herein is unclear to those of ordinary skill in the art as applied to quantities expressing feature sizes, quantities, and physical characteristics, then "about" will be understood to mean within 10% of the specified value. An amount given as about a specified value may be exactly the specified value. For example, if it is not clear to a person of ordinary skill in the art in the context of the use and description in this specification, an amount having a value of about 1 means that the amount has a value between 0.9 and 1.1, and the value can be 1.

All cited references, patents, and patent applications cited above are hereby incorporated by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between the incorporated reference parts and the present application, the information in the preceding description shall prevail.

Unless otherwise indicated, descriptions with respect to elements in the figures should be understood to apply equally to corresponding elements in other figures. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Accordingly, the disclosure is intended to be limited only by the claims and the equivalents thereof.

Claims

1. An optical system, the optical system comprising:

a lens layer comprising a plurality of microlenses arranged along orthogonal first and second directions;

an optically opaque first mask layer spaced apart from the lens layer and defining a plurality of through first openings therein arranged along the first and second directions; and

an optically opaque second mask layer spaced apart from the lens layer and the first mask layer and defining a plurality of through second openings therein arranged along the first direction and the second direction, the first mask layer disposed between the lens layer and the second mask layer, the microlenses and the first openings and the second openings having a one-to-one correspondence therebetween such that, for each microlens, the microlens and the corresponding first opening and second opening are substantially centered on a line at the same oblique angle as the lens layer, wherein when image light carrying an image is incident on the microlens along the line, the image light substantially fills the microlens, greater than about 45% of the incident image light is transmitted by the second opening, and at least one of the first opening and the second opening is sized, in order to reduce image quality degradation due to the microlenses.

2. The optical system of claim 1, wherein the first opening is a physical opening.

3. The optical system of claim 1, wherein the first opening is an optical opening.

4. The optical system of any one of claims 1 to 3, further comprising:

a liquid crystal display extending along the first direction and the second direction;

a light guide disposed to illuminate the liquid crystal display;

a refractive component disposed between the liquid crystal display and the light guide, the refractive component comprising a first prismatic film comprising a first plurality of prisms extending along a first longitudinal direction substantially parallel to the lens layer; and

an optical sensor disposed proximate the light guide opposite the liquid crystal display,

wherein an optical element comprising the lens layer and the first and second mask layers is disposed between the light guide and the optical sensor such that the second mask layer faces the optical sensor.

5. The optical system of claim 4, wherein the refractive component further comprises a second prismatic film adjacent the first prismatic film, the second prismatic film comprising a second plurality of prisms extending along a second longitudinal direction substantially parallel to the lens layer and substantially orthogonal to the first longitudinal direction.

6. An optical layer, comprising:

a structured first major surface and an opposing second major surface, the structured first major surface comprising a plurality of microlenses arranged along orthogonal first and second directions; and

an embedded optically opaque first mask layer disposed between and spaced apart from the first and second major surfaces, the first mask layer defining a plurality of through first openings therein arranged along the first and second directions, there being a one-to-one correspondence between the microlenses and the first openings, wherein for each of at least a majority of the first openings, the first openings define a voided region having a maximum thickness greater than an average thickness of the first mask layer.

7. The optical layer of claim 6, wherein the average thickness of the first mask layer is t, the first openings have an average largest lateral dimension d, and t/d < 0.05.

8. An optical layer, comprising:

an embedded optically opaque first mask layer disposed between and spaced apart from the first and second major surfaces, the first mask layer defining a plurality of through first openings therein arranged along the first and second directions, there being a one-to-one correspondence between the microlenses and the first openings, wherein for each of at least a majority of the first openings, the first openings define a voided region having a top major surface facing the first major surface and an opposing bottom major surface facing the second major surface, wherein in a cross-section of the optical layer substantially perpendicular to the optical layer, the optical layer includes a plurality of nanoparticles concentrated along at least one of the top and bottom major surfaces of the voided region And (4) granulating.

9. The optical layer of claim 8, wherein the first mask layer comprises a first material and the nanoparticles comprise at least one of the first material or an oxide of the first material.

10. An optical layer, comprising:

an embedded optically opaque first mask layer disposed between and spaced apart from the first and second major surfaces, the first mask layer defining a plurality of through first openings therein arranged along the first and second directions, there being a one-to-one correspondence between the microlenses and the first openings, wherein for each of at least a majority of the first openings, the first openings define a voided region having a top major surface facing the first major surface and an opposite bottom major surface facing the second major surface, wherein in a cross-section of the optical layer substantially perpendicular to the optical layer, a spacing of the top and bottom surfaces proximate a center of the voided region is greater than a spacing proximate an edge of the voided region And at least one of the top major surface and the bottom major surface has a surface roughness in a range of 10nm to 200 nm.

11. An optical system, the optical system comprising:

an optical element, the optical element comprising:

a lens layer comprising a plurality of microlenses arranged along orthogonal first and second directions; and

an optically opaque first mask layer spaced apart from the lens layer and defining a plurality of through first openings therein arranged along the first and second directions; there is a one-to-one correspondence between the microlenses and the first openings such that for each microlens, the microlens and the corresponding first opening are substantially centered on straight lines, each straight line being at the same oblique angle to the lens layer; and

a refractive component extending along the first and second directions and disposed proximate the optical element such that, for at least one first light beam incident on the refractive component along a third direction substantially orthogonal to the lens layer, the refractive component splits the first light beam into 2 to 9 beam segments exiting the refractive component along respective 2 to 9 principal directions, a first principal direction of the 2 to 9 principal directions being substantially parallel to each straight line.

12. The optical system of claim 11, wherein the optical element further comprises an optically opaque second mask layer spaced apart from the lens layer and the first mask layer and defining therein a plurality of through second openings arranged along the first direction and the second direction, the first mask layer disposed between the lens layer and the second mask layer, there being a one-to-one correspondence between the microlenses and the second openings such that for each microlens and corresponding straight line, the microlens and corresponding first and second openings are substantially centered on the straight line.

13. The optical system of claim 11, further comprising a photosensor adjacent to the optical element and comprising a plurality of sensor pixels, there being a one-to-one correspondence between the microlenses and the sensor pixels such that, for each microlens and corresponding line, the microlens and corresponding first opening and sensor pixel are substantially centered on the line.

14. The optical system according to any one of claims 11 to 13, further comprising an infrared light source arranged to emit light towards the refractive component in a direction substantially parallel to a second main direction of the 2 to 9 main directions.

15. An optical system, the optical system comprising:

a refractive component extending along orthogonal first and second directions such that, for at least one first light beam incident on the refractive component along a third direction substantially orthogonal to the first and second directions, the refractive component splits the first light beam into 2 to 9 beam segments exiting the refractive component along respective 2 to 9 principal directions, the 2 to 9 principal directions comprising a first principal direction;

an optical element disposed adjacent to the refractive component such that along the first principal direction, but not any other principal direction, at least 45% of light in the beam segment incident on the optical element is transmitted through the optical element;

a light source arranged to emit light in a direction substantially parallel to a second main direction of the 2 to 9 main directions; and

an optical sensor arranged to receive light transmitted through the optical element along the first main direction.